1. Field of the Invention
This invention relates to a magnetic brush developing device for developing an electrostatic latent image formed by an electrophotographic process, and more particularly to a magnetic brush developing device, wherein magnets are used for producing a brush-like bur of a developing agent consisting of iron powder carrier and toner, the aforesaid brush-like bur of developing agent sliding along the surface of latent image, thereby developing same to a visual image.
2. Description of the Prior Art
The magnetic brush developing device has been well known as a developing device for use in a dry type electrophotographic reproducing apparatus and is particularly useful for reproduction of a solid black portion or half-tone portion, rather than the cascade development is.
If the magnetic brush developing device equipped with a single magnetic roller is employed for a high speed reproducing apparatus, it follows that a developing time is compressed, and the feeding of an adequate amount of toner to the latent image is failed, resulting in the unsatisfactory developing in the solid black portion.
Increase in reproduction speed of a reproducing apparatus is the needs of the times. For meeting the requirements, various attempts have hitherto been made, as a result of which there has been proposed a device, in which a plurality of magnetic rollers are employed for compensating for reduction in developing time per roller. In the device, a plurality of developing rollers are provided in vertically paralled relation to one another along the latent image formed surface of a sensitive member. The device, however, suffers from the drawbacks that when a developing agent fed to the preceding developing roller is fed successively to the succeeding rollers, uniform delivery of the developing agent between the adjacent rollers is failed, resulting in the concentration of the developing agent to only a single roller, the local accummulation of the developing agent or leakage to the outside of the developing device.